Numerous attempts have been made to formulate laundry detergent compositions which provide the good cleaning performance expected of them and which also have good textile softening properties. Attempts have been made to incorporate cationic textile softeners in anionic surfactant-based built detergent compositions employing various means of overcoming the natural antagonism between the anionic and cationic surfactants. For instance, U.S. Pat. No. 3,936,537, Baskerville et al., issued Feb. 3, 1976, discloses detergent compositions comprising organic surfactant, builders, and, in particulate form (10 to 500 microns), a quaternary ammonium softener combined with a poorly water-soluble dispersion inhibitor which inhibits premature dispersion of the cationic in the wash liquor. Even in these compositions some compromise between cleaning and softening effectiveness has to be accepted. Another approach to provide built detergent compositions with softening ability has been to employ nonionic surfactants (instead of anionic surfactants) with cationic softeners. Compositions of this type have been described in, for example, German Pat. No. 1,220,956, assigned to Henkel, issued Apr. 4, 1964; and in U.S. Pat. No. 3,607,763, Salmen et al., issued Sept. 21, 1971. However, the detergency benefits of nonionic surfactants are inferior to those of anionic surfactants.
Other laundry detergent compositions have employed tertiary amines along with anionic surfactants to act as textile softeners. British Pat. No. 1,514,276 Kengon, published June 14, 1978, employs certain tertiary amines with two long chain alkyl or alkenyl groups and one short chain alkyl group. These amines are useful as fabric softeners in detergent compositions when their isoelectric point is such that they are present as a dispersion of negatively charged droplets in the normally alkaline wash liquor, and in a more cationic form at the lower pH of a rinse liquor, and so become substantive to fabrics. The use of such amines, among others, in detergent compositions has also been previously disclosed in British Pat. No. 1,286,054, assigned to Colgate-Palmolive, published Aug. 16, 1972.
Another approach to provide anionic detergent compositions with textile softening ability has been the use of smectite-type clays, as described in U.S. Pat. No. 4,062,647, Storm et al., issued Dec. 13, 1977. These compositions, although they clean well, require large contents of clay for effective softening. The use of clay together with a water-insoluble cationic compound in an electrically conductive metal salt as a softening composition adapted for use with anionic, nonionic, zwitterionic and amphoteric surfactants has been described in British Pat. No. 1,483,627, assigned to Procter & Gamble, published Aug. 24, 1977.
Laundry detergents containing imidazolines have been disclosed before. See, for example, U.S. Pat. No. 4,589,988, Rieck et al., issued May 20, 1986, which discloses granular laundry detergents containing a combination of surfactant, and a softener system comprising amine or imidazoline and a phyllosilicate. The amine or imidazoline component is adsorbed onto the clay silicate particles. U.S. Pat. No. 4,294,710, Hardy, et al., issued Oct. 13, 1981, discloses granular laundry detergents containing a combination of surfactants along with tertiary amines or imidazoline derivatives. Generally, such detergent compositions are prepared such that the amine is sprayed onto the particulate detergent components. This reference does not recognize the criticality of particle size of the imidazoline for imparting fabric care benefits.
It is therefore an object of the present invention to provide a laundry detergent containing surfactant and imidazoline particles with an average particle size diameter of from about 20 to about 200 microns, which provides excellent through-the-wash fabric care benefits without impairing cleaning performance. Such fabric care benefits include static control and fabric softening.